A crane boom, such as one comprising a plurality of nested, telescoping sections, typically includes an auxiliary boom section called a “fly” comprised of welded tubular and plate structures. This fly can be used to extend the reach of the crane when moved from a stowed position alongside of the boom to an inline condition. In order to position the fly in this manner, or re-position it when not in use, a sequence of inserting and removing pins must be precisely followed, or else the fly can inadvertently become detached from the boom.
Others have proposed complicated systems for engaging the pins to prevent removal in the incorrect sequence. However, such systems are subject to failure based on misuse (such as if too much force is applied to the pin to cause it to drive through any blocking element intended to stop the improper insertion or removal). Known past systems are also not intuitive, and can still lead the operator to attempt to remove the pins in the incorrect sequence, thus wasting time and effort and potentially leading to the inadvertent detachment of the fly.
Accordingly, a need exists for an improved and simplified system which eliminates the aforementioned issues and others not yet discovered. The system would operate such that the condition of the fly relative to the boom can be easily determined, such that time and effort is not wasted attempting to perform an incorrect sequence of operations to pivot the fly to the operative condition. The system would also make the pin insertion and removal sequence intuitive, so that even an unfamiliar operator may perform the steps in the correct order without uncertainty.